Added constraint support for CollectionEntitySet

[mvanbeselaere]

This commit answers a specific requirement we had where we needed custom CollectionEntitySets to follow relationship constraints. Found out constraints where only working with SqlEntitySet, so I updated the code by altering the Transaction's filter with a manual constraint injection.

This is probably not the best way to implement it, but this could initiate a discussion on this feature here.

Have a good one!